Handheld computers, typically referred to as personal digital assistants (PDAs), are intended to be mobile devices. In general, small sizes are desired for handheld computers to enhance mobility. However, there are constraints to how small a handheld computer can be for convenience of the user. In particular, certain characteristics of handheld computers require a minimum amount of space on the exterior housing of the handheld computer.
Most handheld computers require a minimum size display. The minimum display size is set by balancing considerations such as mobility with the need for the user to view data, such as personal management information, pictures, and text pages. For some handheld computers, the size of the display may also need to be large enough to provide a character input mechanisms for the user. For example, some handheld computers incorporate character recognition logic as a primary means for the user to enter character data into the handheld computer. The displays for the handheld computer may be made to be contact-sensitive. A portion of the display may be combined with logic to provide an immediate character recognizer for recognizing gestures or strokes entered onto a portion of the display as characters. Other displays may be used to display a virtual keyboard. The immediate character recognition regions and virtual keyboards require the displays to be of a minimum size to support those kinds of character entry.
The size of the handheld computer typically must also accommodate mechanical actuators, such as buttons or pivot switches. These are typically placed on the same surface where the display is viewable to enable users to coordinate button actions with what is shown on the display.
As battery and printed circuit board technology becomes more advanced, the display size and mechanical actuators are increasingly becoming the primary factors that determine the size of the handheld computer. Reducing the length of the handheld computer requires sacrificing features of the display and/or buttons.
Sometimes the functionality from two different devices is combined into one unit. But combining devices such as handheld computers with other devices generally leads to a device that is larger than a device having the functionality of only one device. Usually, this is because each type of device has a particular set of hardware features that are exposed on the device. The physical presence of hardware features for each type of device cannot be eliminated when two or more different types of devices are combined.